The present invention relates to covers or tarping systems for open-topped containers. The invention concerns an apparatus for pivotably mounting a flexible cover over the bed of a truck, such as a dump truck, and more specifically to an actuation mechanism for pivoting the cover over the truck bed.
Some hauling vehicles, such as dump trucks, include open-topped containers used for hauling or storing various materials. For example, in a typical dump truck application, the dump body is used to haul a variety of particulate material, such as gravel, aggregate or similar products. In addition, some hauling vehicles carry organic materials, such as grain or produce.
Depending upon the nature of the materials stored in the open-topped container, it is often desirable to provide a cover for the container. Of course, rigid covers are well known that may be hinged from one end of the container body. These rigid covers have gradually given way in the industry to flexible tarping systems because the flexible tarpaulin can be easily stowed when a cover is not necessary, such as when the dump bed is being loaded. Moreover, the flexible tarp is much easier to deploy than a rigid cover.
A variety of tarping systems have been developed that are geared to particular hauling vehicle applications. One such tarping system for use with dump trucks is the EASY PULL(copyright) Tarping System of Aero Industries, Inc. The EASY PULL(copyright) System includes a flexible tarp that is wound around a spool at one end of the dump bed. A rope attached to the free end of the tarp can be used to unwind the tarp from the roller to span the length of the dump bed.
Another cover system particularly suited for open-topped containers on hauling vehicles, is the EASY COVER(copyright) Tarping System, also of Aero Industries, Inc. The EASY COVER(copyright) Tarping System includes a U-shaped bail that is pivotably mounted at its ends to the base of the container body. The horizontal section of the U-shaped bail is attached to the tarp, while the free ends of the vertical elements are pivotably mounted. In one application, the EASY COVER(copyright) Tarping System allows the tarp to be manually pulled in a sweeping arc over the container load.
In another application of the EASY COVER(copyright) System, an actuation mechanism is provided that automatically pivots the U-shaped bail member to deploy the tarp over the load within the open-topped container. When the actuation mechanism is released, it automatically pivots the bar, thereby unfurling the tarp from the tarp roller at the front of the vehicle. A hand crank or powered motor can be provided to rotate the tarp roller to wind the tarp when it is desired to open the container top. The hand crank or motor mechanism must be capable of providing sufficient mechanical advantage to overcome the deployment force of the actuation mechanism.
A vehicle 10 is depicted in FIG. 1 having an open-topped body 13. As illustrated in FIG. 1, the vehicle can be a dump truck, with the open-topped container comprising a dump body. A tarpaulin cover 16 is shown in its deployed configuration spanning the length of the container and covering the load within. The tarp cover 16 can be wound onto a tarp roller 19. Both the tarp cover 16 and the roller 19 can be of a variety of known constructions, such as the EASY COVER(copyright) Tarping System.
A bail member 22 is connected to one end of the tarp cover 16 in the manner described above. The bail member is pivotably mounted to the truck body 13 by way of an actuation mechanism 25. This actuation mechanism can take a variety of forms in the prior art. For instance, one such mechanism relies upon extension springs that apply a linear force at some point along the bail member 22, to cause the bail member to pivot when the tarp roller 19 is released. In a similar configuration, a compression spring is used to push the bail member outward, thereby pivoting it about its pivot mount at the base of the truck body 13.
In other applications, a coil torsion spring applies a torque or moment to the lower ends of the U-shaped bail member 22. One advantage of the coil torsion spring is that it can be mounted substantially under the truck body 13 so that the actuation mechanism is clear of the working area around the truck body. In some instances, an under-body mount cannot be accomplished. In these instances, a spiral torsion spring assembly can be used to apply torque at the pivot mount of the bail member 22.
Spiral torsion springs are also used in bow base/bow extension applications. Here, a bow base element coupled with a bow extension element act as a bail member. The bow base attached to the truck body is connected to a bow extension attached to the truck cover. One or more spiral torsion springs is used in the coupling between the bow base and bow extension members.
One such spiral torsion spring of the prior art is depicted in FIGS. 2 and 3. In particular, the actuation mechanism 25xe2x80x2 is mounted to the vehicle bed by a mounting plate 27. The actuation mechanism 25xe2x80x2 includes a post 29 that projects from the mounting plate 27. The post is configured to extend through openings at the pivot mount for the bail member 22xe2x80x2. A torsion spring pack 31 is disposed within the pivot end 23xe2x80x2 of the bail member 22xe2x80x2.
As shown most clearly in FIG. 3, the spring pack 31 can include a number of individual springs, such as torsion spring 31a. Each spring includes an anchor end 33 that is configured to fit within an anchor groove 35 defined along the length of the post 29. The opposite end of the torsion spring constitutes a reaction end 37 that reacts against a post 39 extending through the interior of the bail member 22xe2x80x2.
With any of the various actuation mechanisms described above, the amount of force generated by the mechanism depends upon the nature of the tarp cover 16 and the length that it must reach in its deployed position. Obviously, the longer the open-topped body 13, the longer distances the tarp cover 16 must cover. This translates to longer arms for the bail member 22. The longer the arms, the stronger the force or torque needed to pivot the arms from the stowed to the deployed position.
In order to generate this increased force using a spiral torsion spring configuration, such as that shown in FIGS. 2 and 3, additional springs, such as spring 31a, must be added to the spring pack 31. In one typical prior art spiral spring system, between three and six such springs are utilized, depending upon the length of the bail member arms. In the configuration depicted in FIG. 2, four such springs are provided. Each of the springs is aligned axially along the length of the post 29. Obviously, additional springs added to the pack 31 would require a longer post 29.
It has been found in practice that any spring pack using more than three springs projects too far from the side of the vehicle body 13. This excessive projection presents two problems: (1) since the arms of the bail member 22 necessarily project farther from the side of the body 13, they are more easily struck or damaged; and (2) federal law prohibits tarping system hardware from exceeding three inches from the side of the truck body. Since each spiral torsion spring is typically about one inch in width, it can be easily be appreciated that no more than three such springs can fit within the federally mandated envelope.
Consequently, there remains a need for an actuation mechanism that can utilize spiral torsion springs for a wide range of bail member dimensions, while still avoid the problems of the prior art system shown in FIGS. 2 and 3.
In order to address this unresolved need, the present invention contemplates a spiral torsion spring configuration that incorporates two spring coils within the same envelope. In one feature of the invention, the spring is a double coil spring in which two concentrically wound coil portions are connected at a center anchor portion. An actuation mechanism according to a preferred embodiment of the invention includes a shaft defining an elongated slot that is configured to receive the center anchor portion of a number of such double coil springs.
The actuation mechanism can further include a housing that surrounds the double coil springs and mates with a pivot end of an arm of the bail member. Each coil portion of each spring terminates in a reaction end that is configured to engage a post passing through the housing. In the preferred embodiment, two such posts are situated within the housing at diametrically opposite positions. Each spring element, then, includes a left coil portion and a right coil portion, each having a corresponding reaction end that contacts a respective one of the diametrically opposite posts. Thus, each coil portion can exert a torsional force against each post, which results in a pivoting moment being applied to the arms of the bail member through the housing.
In one aspect of the actuation mechanism, the housing can include a male and a female half that are connected together about the double coil springs. The two halves can be combined to define a pair of peg holes at diametrically opposite sides of the housing. The set of peg holes mate with similar pairs of pegs projecting from the pivot end of the arms of the bail member when the housing halves are clamped about the pivot end. The pegs and peg holes hold the bail member arms to the housing.
Alternatively, the bail member arm can be of a tubular design wherein the arm attachment portion of the housing is inserted into the bail member arm. In this case, the bail member also has a pair of holes that mate with the peg holes in the housing. A pair of bolts or other suitable fasteners can be used to secure the arm to the housing.
Each housing half can also define a shaft bore through which the slotted shaft extends. Preferably, the shaft projects from a mounting plate that can be mounted to the open-topped container to support the actuation mechanism. A pair of bushings can be disposed between the shaft and the housing halves to reduce friction as the housing rotates about the shaft under the torsional force applied by the double coil springs. The free end of the shaft projects beyond the housing and can receive a retaining ring to hold the housing on the shaft.
Likewise, the reaction posts can extend through reaction bores defined in the male and female housing halves. In one embodiment, the reaction posts include an enlarged head at one end and receive a retaining ring at the other end to hold the reaction posts within the housing.
In an alternative embodiment, the male and female housing halves can have the reaction posts fixed to the interior of the housing halves. Preferably, each housing half can have half of each post cast into the housing half. The posts in this embodiment can include a web of material connecting the length of the posts to one side of the housing halves for added strength, giving the posts a keyhole type cross section. In this configuration, the male and female halves can be held together with screws or other suitable fasteners.
In one aspect of the invention, the double coil springs reduce by half the number of spiral torsion springs required to achieve a desired deployment torque. Thus, when six prior art torsion springs are called for, only three double coil springs of the present invention are required. Each double coil spring can be formed of wound flat stock, with the number of windings of each coil portion being determined by the desired torsional force. Preferably, the flat stock has a width of about one inch or less, so a combination of three double coil springs easily falls within the federally mandated prominence guidelines.
In another aspect of the invention, the actuation mechanism is adapted for use as a knuckle joint with a bow base and bow extension cover system. In embodiments of this aspect, the housing can mate with either the bow base or the extension member with the pivot shaft attached to the other. Here, the torsional force generated by the spring coils results in pivoting movement of the bow base and bow extension relative to each other.
It is one object of the present invention to provide an actuation mechanism for use in deploying a cover over an open-topped container. A more particular object is to provide such a mechanism for use with a flexible tarping system for a vehicle, such as a dump truck.
One advantage achieved by the present invention over prior art devices is that a requisite amount of deployment torque can be generated by a spring pack that fits within an acceptable envelope. A further benefit is that the number of parts that must be assembled to form the actuation mechanism is reduced.